/**
 * 该模块提供无序散列集合所需要的一些辅助函数。
 * 仅供内部使用。
 * License: BSD
 * Authors: Lucifer (786325481@QQ.com)
 * Copyright: Copyright (C) 2008 Lucifer. All rights reserved.
 */
module system.collections.PrimeHelper;

import system.math.Math;

package invariant int[72] PrimeArray = [3, 7, 11, 17, 23, 29, 37, 47, 59, 71, 89, 107, 131, 163, 197, 239, 293, 353, 431, 521, 631, 761, 919,
									1103, 1327, 1597, 1931, 2333, 2801, 3371, 4049, 4861, 5839, 7013, 8419, 10103, 12143, 14591,
									17519, 21023, 25229, 30293, 36353, 43627, 52361, 62851, 75431, 90523, 108631, 130363, 156437,
									187751, 225307, 270371, 324449, 389357, 467237, 560689, 672827, 807403, 968897, 1162687, 1395263,
									1674319, 2009191, 2411033, 2893249, 3471899, 4166287, 4999559, 5999471, 7199369];

package bool isPrime(int numeric)
{
	if((numeric & 1) != 0)
	{
		int top = cast(int)(sqrt(cast(double)numeric));
		for(auto divisor = 3; divisor <= top; divisor += 2)
		{
			if((numeric % divisor) == 0)
				return false;
		}
		return true;
	}

	return (numeric == 2);
}

package int getNextPrime(int numeric)
in
{
	assert(numeric >= 0);
}
body
{
	for(auto i = 0; i < PrimeArray.length; i++)
	{
		if(numeric <= PrimeArray[i])
			return PrimeArray[i];
	}

	for(auto i = (numeric | 1); i < int.max; i += 2)
	{
		if(isPrime(i))
			return i;
	}
	return numeric;
}
